linux: update to sdk v1.6 release
1.move more generic bits to linux-qoriq-sdk.inc file
2.add support for multiple kernel delta config files
3.Append SDK_VERSION to .scmversion, and use the same version format
with u-boot. For exmaple: 3.12.17-rt25-QorIQ-SDK-V1.6+gfae7d11
4.add linux-qoirq-sdk_3.12.bb to use latest released codes in sdk v1.6, detailed changes can be viewed at:
http://git.freescale.com/git/cgit.cgi/ppc/sdk/linux.git/log/?qt=range&q=
c29fe1a733308cbe592b3af054a97be1b91cf2dd
Signed-off-by: Ting Liu <b28495@freescale.com>
